$.ajax({
   beforeSend:function(){
   // handle the beforeSend event   
   },
   complete:function(){
// handle the complete event  
   }
});

$.ajax({
type:"post",
data:studentInfo,
contentType:"application/json",
url:"/Home/Submit",
beforeSend:function(){
   //禁用按钮防止重复提交
   $("#submit).attr({disabled:"disabled"});
},
success:function(data){
   if(data=="Success"){
     // 清空输入框
     clearBox();
   }
},
complete:function(){
   $("#submit").removeAttr("disabled");
},
error:function(data){
   consloe.info("error:"+data.responseText);
}
});

$.ajax({
type:"post",
contentType:"application/json",
url:"/Home/GetList",
beforeSend: function(){
   $("loading").show();
},
success: function(data){
   if (data=="Success"){
     // ...
   }
},
error: function(){
   console.info("error:"+data.responseText);
}
});